One thing I have though about regarding the balancing is and niches of the races is where the baseline is. Because 15 is the best you can buy and +1 racial bonuses are really common, it means that 16 in the main stat is pretty damn easy to get. There are many races that can give that 16 in your desired stat and all humans can get it. This makes 16 mentally the expected baseline, and can easily feel that if you can't get that you're punished, your character is weaker than they 'should.' This is unfortunate.
I suspect that if point buy cap was either 14 or 16, so that only way to get better bonus than others was to have +2 from the race, it would feel less like you're 'bad' if you don't have it as that +2 would be pretty rare. (You would however need to prohibit variant humans from stacking their possible feat ability bonus with their other +1s, or otherwise they could again max any stat.) Or maybe it would just lead to everyone pigeonholing to those +2 races even more. I don't know.